Fist off the pic above is the wrong way to "twist" the wire :-p
( thats a lot of soder on that )
2nd.
Ciruit sells wiring harness kits which is PLUG and PLAY for factory harnesses and the other end to the radio( called smart harness). In 98% of the time there is no need to splice into the harness. IF the kit is not available they can order it or with customer ok they will splice into the harness but they charge to do it.
I want to open thta harness up and see how the wires were done. If they were sodered right and wrapped with tape there is no issue.
Fire hazard. LOL. Take your car to a dealership they will do the same thing if there is a problem with the wiring, that or they will use BUTT CONNECTORS.
3rd. Having to "make room" for a radio. happens on a lot of cars.
Grand prixs, regals, monte, impalas. you have to break off the plastic part in the back. There are very few radios out that are short enough to clear it.
I used to supervise the roadshop at circuit. Yes there were some bad installs. But the only way that would be a fire hazard if they did not soder and over time the wire worked lose, came out of the electrical tape and found its way to a ground. ( He used stock radio harness so it is fused) so this is very very unlikely. If it did i would be back at honda because the fuse panel did not do its job.